I got a tweed Blues Jr. about 9 months ago, and recently it's been acting up. Whenever I turn it on, it starts making some crazy popping/crackling noises, and the actual guitar sound will fade in and out. After about 2-3 minutes of being on, it works fine and sounds great. I know the problem is in between the "volume" and "master" knobs, but that's about all I can figure out with my limited knowledge. Can anyone lend a hand?